Study of the Efficacy and Safety of Lemborexant in Subjects 55 Years and Older With Insomnia Disorder (SUNRISE 1)

Inclusion Criteria

• Male age 65 years or older or female age 55 years or older at the time of informed consent
• Meets the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition criteria for Insomnia Disorder, as follows:
• Complains of dissatisfaction with nighttime sleep, in the form of difficulty staying asleep and/or awakening earlier in the morning than desired despite adequate opportunity for sleep (Note that if the complaint is limited to difficulty initiating sleep, the participant is not eligible)
• Frequency of complaint ≥ 3 times per week
• Duration of complaint ≥ 3 months
• Associated with complaint of daytime impairment
• History of subjective wake after sleep onset (sWASO) typically ≥ 60 minutes on at least 3 nights per week in the previous 4 weeks
• Reports regular time spent in bed, either sleeping or trying to sleep, between 7 and 9 hours
• Reports habitual bedtime, defined as the time the participant attempts to sleep, between 21:00 and 24:00 and habitual waketime between 05:00 and 09:00
• Insomnia Severity Index (ISI) score ≥ 13
• Confirmation of current insomnia symptoms as determined from responses on the Sleep Diary before the second screening visit
• Confirmation of regular bedtime and waketime as determined from responses on the Sleep Diary
• Confirmation of sufficient duration of time spent in bed, as determined from responses on the Sleep Diary
• Objective (polysomnography [PSG]) evidence of insomnia as follows:

a) Wake after sleep onset (WASO) average ≥ 60 minutes on the 2 consecutive PSGs, with neither night 15 (scores of 11 to 15 require excessive daytime sleepiness to be recorded in participant's Medical History)

• Reports symptoms potentially related to narcolepsy, that in the clinical opinion of the investigator indicates the need for referral for a diagnostic evaluation for the presence of narcolepsy
• On the Munich Parasomnia Scale (MUPS), endorsed the item that corresponds to a history of sleep-eating or reports a history of sleep-related violent behavior, sleep-driving, or symptoms of another parasomnia that in the investigator's opinion make the participant unsuitable for the study
• Apnea-Hypopnea Index > 15 or Periodic Limb Movement with Arousal Index >15 as measured on the PSG at the second screening visit
• Beck Depression Inventory - II (BDI-II) score >19 at Screening
• Beck Anxiety Index (BAI) score >15 at Screening
• Habitually naps during the day more than 3 times per week
• Is a female of childbearing potential Note: All females will be considered to be of childbearing potential unless they are postmenopausal (defined as amenorrheic for at least 12 consecutive months, and are postmenopausal without other known or suspected cause), or have been sterilized surgically (i.e., bilateral tubal ligation, total hysterectomy, or bilateral oophorectomy, all with surgery at least 1 month before dosing).
• Excessive caffeine use that in the opinion of the investigator contributes to the participant's insomnia, or habitually consumes caffeine-containing beverages after 18:00 and is unwilling to forego caffeine after 18:00 for the duration of his/her participation in the study.
• History of drug or alcohol dependency or abuse within approximately the previous 2 years
• Reports habitually consuming more than 14 drinks containing alcohol per week (females) or more than 21 drinks containing alcohol per week (males), or unwilling to limit alcohol intake to no more than 2 drinks per day or forego having alcohol within the 3 hours before bedtime for the duration of his/her participation in the study
• Known to be positive for human immunodeficiency virus
• Active viral hepatitis (B or C) as demonstrated by positive serology at Screening
• A prolonged QT/QTcF interval (QTcF >450 milliseconds [ms]) as demonstrated by a repeated electrocardiogram (ECG) at Screening (repeated only if initial ECG indicates a QTcF interval >450 ms)
• Current evidence of clini